Primary exercises
- Manually created factor.
In a study participants were asked whether their sport activity is none, oncePerWeek, severalPerWeek or daily.
Build a proper factor for the responses below and store it in a variable w.
Print the factor.
Write the code to count the numbers of occurrences of each level and print the counts.
severalPerWeek, none, none, oncePerWeek, oncePerWeek, oncePerWeek, oncePerWeek, ?, none, none
v <- c( "severalPerWeek", "none", "none", "oncePerWeek", "oncePerWeek", "oncePerWeek", "oncePerWeek", NA, "none", "none" )
w <- factor( v, levels = c( "none", "oncePerWeek", "severalPerWeek", "daily" ) )
w
[1] severalPerWeek none none oncePerWeek oncePerWeek oncePerWeek oncePerWeek <NA> none none
Levels: none oncePerWeek severalPerWeek daily
fct_count( w )
# A tibble: 5 x 2
f n
<fct> <int>
1 none 4
2 oncePerWeek 4
3 severalPerWeek 1
4 daily 0
5 <NA> 1
- A factor with a random content.
Read help about the function sample.
Then study and try the following lines of code to understand the results.
Next, understand why an error is generated and use replace argument to generate a vector with 100 samples.
Store this vector in a variable v and build a factor w from it.
Finally, count the numbers of occurrences of each level in w.
Ensure, that levels are in order provided in the variable lvl.
lvs <- c( "none", "oncePerWeek", "severalPerWeek", "daily" )
sample( lvs, 3 )
[1] "daily" "severalPerWeek" "oncePerWeek"
sample( lvs, 3 )
[1] "oncePerWeek" "severalPerWeek" "daily"
sample( lvs, 3 )
[1] "daily" "severalPerWeek" "none"
sample( lvs, 100 )
Error in sample.int(length(x), size, replace, prob): cannot take a sample larger than the population when 'replace = FALSE'
v <- sample( lvs, 100, replace = TRUE )
w <- factor( v, levels = lvs )
w
[1] none daily none daily oncePerWeek oncePerWeek severalPerWeek none severalPerWeek oncePerWeek none none
[13] severalPerWeek oncePerWeek oncePerWeek severalPerWeek daily oncePerWeek severalPerWeek none severalPerWeek severalPerWeek oncePerWeek none
[25] daily daily none severalPerWeek daily oncePerWeek daily oncePerWeek severalPerWeek severalPerWeek none oncePerWeek
[37] none severalPerWeek oncePerWeek none severalPerWeek severalPerWeek severalPerWeek severalPerWeek daily none severalPerWeek daily
[49] daily daily oncePerWeek none oncePerWeek daily severalPerWeek daily oncePerWeek oncePerWeek none oncePerWeek
[61] daily daily none severalPerWeek none oncePerWeek daily oncePerWeek severalPerWeek daily none oncePerWeek
[73] none daily severalPerWeek none none daily none oncePerWeek severalPerWeek none oncePerWeek oncePerWeek
[85] none oncePerWeek none oncePerWeek oncePerWeek daily daily daily none oncePerWeek severalPerWeek severalPerWeek
[97] oncePerWeek oncePerWeek none none
Levels: none oncePerWeek severalPerWeek daily
fct_count( w )
# A tibble: 4 x 2
f n
<fct> <int>
1 none 27
2 oncePerWeek 28
3 severalPerWeek 23
4 daily 22
- Reordering factor levels.
When a factor is shown on an axis of a plot, the order is given by its levels.
The factor w from the previous exercise will be then shown in this order: none, oncePerWeek, severalPerWeek, daily.
But for a picture in a manuscript the following order might be needed: daily, severalPerWeek, oncePerWeek, none.
Apply to w one of the fct_ functions from the tidyverse library to produce a factor w2 with the requested order.
Show the levels of w2.
Again show the number of elements of each level in w2 and compare it with the table of the previous exercise.
w2 <- fct_relevel( w, c( "daily", "severalPerWeek", "oncePerWeek", "none" ) )
levels( w2 )
[1] "daily" "severalPerWeek" "oncePerWeek" "none"
fct_count( w2 )
# A tibble: 4 x 2
f n
<fct> <int>
1 daily 22
2 severalPerWeek 23
3 oncePerWeek 28
4 none 27